I don't think that there are any spoilers but I could possibly see this happening in season 5.
There was a knock on his door, hand still in a cereal box he leaned out his kitchen and opened the door. He stepped back in surprise when he saw his partner Temperance Brennan standing on the other-side.
"Bones?....uh…come in" He stammered. Taking his hand out of the cereal box and placing the box on the counter. Brennan stood in his doorway, she didn't say anything. Booth was uncomfortable with the silence; she had been ignoring him for two weeks now, two very painful weeks.
"I…I don't know why I am here." She said finally, studying her shoes. "I just…I felt like I needed to see you. I wanted to…to make sure we were ok." Booth stared at her for a moment.
He sighed, "No, Bones, we're not ok" She looked up, fear evident in her eyes but otherwise her face was stoic.
"Maybe you could you know come in and we could talk?" He suggested as lightly as he could. Brennan hesitated a moment longer than stepped through the door and closed it behind her.
"Do you want a beer?" Booth asked
"No, I think we should stay clear-headed for this conversation Booth." She replied clinically. Booth nodded and led the way to his couch.
"I'm sorry Booth" Brennan started almost as soon as they sat down. "It's my fault that we are in such a mess…"
"Bones stop. You were the one who wanted to keep everything professional; it's my fault for suggesting more." Booth said quickly.
"I was, I am scared Booth."
"I know, I knew you weren't ready to hear it, but I couldn't hold it in any longer. I was hoping that maybe after you thought about it for a little bit we would be ok, but I guess I was wrong."
"Sweets is threatening to split us up because of this."
"I know." He said sadly "It's the last thing I want to happen."
"I don't want to get split up. And I was scared that if we started a more personal relationship that we would get split up, and I think that our work is too important to risk it." She said. He looked hurt but tried to quickly cover it up. She saw it for a fraction of a second and looked back down at her shoes.
"I am not good at relationships. I can't commit. Monogamy is against human nature, being with one person forever is a foreign concept preserved by society and is romanticized by society in order to create certain behavioral morals."
"So what you are saying is because of anthropology you don't want to give us a try."
"Yes. It is a fact that most relationships do no last and I wouldn't be able to live with myself if I hurt you because I can't commit and think that monogamy is against our nature. I wouldn't be able to live without you in my life, as my best friend, my rock. And I don't want to risk that. I don't want that to go away." Booth looked at her and nodded.
"Some things are worth the risk Bones. You can't live your life not taking any risks."
"I can't risk this Booth."
"You don't want to risk giving us a chance….what if you regret it?"
"I don't regret things, regret is an irrelevant and useless emotion, you can't change your decision once you have made it. It would be illogical to regret something."
"So if I hypothetically get married one day to some other woman, you are not going to be sad or jealous or regret not giving us a chance knowing that we have the potential to make it?" Booth asked calmly.
"I would be sad, very sad and jealous but I would have to live with my decision."
"No regrets?" Brennan didn't say anything; he took that as a yes she would have regrets.
"I can't Booth. I can't give you what you want….not…not right now."
"For how long?"
"As long as it takes for you to be ready"
"What if I am never ready?"
"You will be one day"
"Why do you always say things like that? Everything happens eventually, I'll believe in love someday, I will be one day?"
"Because I have to. It's not only for you Bones. I need to believe that too." Booth said, now it was his turn to examine his shoes. Brennan looked at him. It was suddenly clear to her how much her resistance and stubbornness was affecting him. He said that he needed to believe that someday she would be able to love him; someday she would be ready for a real relationship because otherwise he would be completely heart-broken and it would be her own fault. She didn't ask him to fall in love with her, it happened, she was the one telling him that she couldn't let it happen, she couldn't let him be happy, let herself be happy with him because she was scared.
"I think I am gonna go." She said getting to her feet. Booth looked up at her, she saw the love and hurt in his eyes.
"We will be ok, won't we?" She didn't think that she could bear it if they weren't.
"I hope so Bones, I hope so." Booth replied softly getting to his feet.
"I'll see you tomorrow then? Lunch at the diner?" She asked trying to make some amends. Booth smiled slightly, a small derivative of his charm smile but it was more than she had seen in over two weeks.
"Ya. Lunch at the diner" He said. He wanted to hug her but didn't. She wanted him to hug her but knew that he wouldn't. He would think that she didn't want that kind of intimacy since she was rejecting him.
"Ok…bye then." She said opening his door and stepping out.
"Bye" He said as she closed it behind her. He pressed his back against the door and sighed. "Someday" He though hopefully.